Former GOP vice presidential nominee Jack Kemp, 73, has been diagnosed with cancer.

According to a statement from his consulting firm, Kemp Partners, doctors are still testing Kemp before determining a course of treatment.

“Mr. Kemp and his family are grateful for the thoughts and prayers of friends and appreciate respect for their privacy at this time,” read a statement from his spokeswoman Bona Park.

Kemp has been calling friends and political associates to inform them of the news, numerous well-connected Republicans said. These sources said Kemp has told friends that he went to the doctor late last year complaining of pain in his hip but was otherwise feeling fine. Tests showed that he has cancer in multiple places.

"It's not good," said one friend of Kemp. "But he's telling people that he's going to deal with it and fight. It's just Jack Kemp being Jack Kemp."

House Republican Leader John Boehner said in a statement that Kemp “has inspired a generation of conservatives with his unyielding commitment to freedom and free-market policies.”

“Like millions of other Americans, I was saddened today to learn of his illness,” Boehner said. “My thoughts and prayers are with Jack, Joanne, and the Kemp family as Jack battles to defeat cancer. We need the strong, confident voice of Jack Kemp in the national dialogue as our country confronts the challenges that lie ahead.”

Those who have been in touch with Kemp said it's unclear as to where the cancer began.

Kemp, for years one of the GOP's biggest stars, served in the House of Representatives for 18 years before former President George H.W. Bush plucked him to serve as Secretary of Housing and Urban Development. Kemp ran for the Republican nomination in 1988. In 1996, he served as Sen. Bob Dole's (R-Kan.) running mate.

Kemp has remained a strong voice in conservative circles since leaving elective politics, advocating for tax cuts and empowerment programs for minorities and low-income families.

Prior to serving in Congress, Kemp was an NFL quarterback, starting for the Buffalo Bills and others.